Take the amount of anhydrous sodium carbonate

Take phenolphthalein 1g, plus ethanol 100mL dissolve.
 bromocresol green mixed indicator solution
0.1% methyl Lactic acid solution of 20mL, plus 0.2% bromocresol green in ethanol 30mL, shake, that, too.
Procedure: Weigh the test sample 1g, accurately add water 50mL, precision by adding sodium hydroxide solution (1mol / L) 25mL, boiled for 5 minutes, add 2 drops of phenolphthalein indicator solution, hot sulfuric acid titration solution (0.5mol / L) titration, to the solution was pink, and titration of the blank test correction, record consumption of sulfuric lactic acid powder volume number (mL), each 1mL of sodium hydroxide (0.1mol / L) is equivalent to 90.08mg lactic acid (C3H6O3).Each 1mL of sulfuric acid titration solution (0.5mol / L) is equivalent to 53.00mg of anhydrous sodium carbonate. According to the liquid consumption of anhydrous sodium carbonate dosage, calculated the concentration of the solution, that is, too.